Bischler−Napieralski Cyclization−<i>N</i>/<i>C</i>-Alkylation Sequences for the Construction of Isoquinoline Alkaloids. Synthesis of Protoberberines and Benzo[<i>c</i>]phenanthridines <i>via</i> C-2‘-Functionalized 3-Arylisoquinolines<sup>1</sup>
作者:Nuria Sotomayor、Esther Domínguez、Esther Lete
DOI:10.1021/jo960007s
日期:1996.1.1
regioselectively yielded 2,3-disubstituted 13,14-dihydroprotoberberinium salts 20, a scarcely studied oxidation state in this class of alkaloids. Subsequent reduction of the iminium bond gave the known coralydine (21a) and O-methylcorytenchirine (21b) and their 8-phenyl analogue 21c. The one-pot preparation of these dihydroprotoberberinium salts 20 is shown to proceed with cleavage of the silyl ether and immediate
据报道,有效合成路线为原小ber碱和苯并[c]菲啶类的异喹啉生物碱。关键的转化来自于C-2'-官能化的N-(1,2-二芳基乙基)酰胺或烯酰胺经过3-芳基异喹啉衍生物的分子内环化作用。因此,在Bischler-Napieralski反应条件(PCl(5),腈作为溶剂,室温)下,N-(1,2-二芳基乙基)酰胺12区域选择性地生成2,3-二取代的13,14-dihydroprotoberberinium盐20这类生物碱中的氧化态。随后亚胺键的还原得到已知的珊瑚素(21a)和O-甲基二十碳五烯碱(21b)及其8-苯基类似物21c。已显示一锅制备这些二氢pro小ber碱盐20时先裂解甲硅烷基醚并立即卤化所得羟基,然后将所得N-(1,2-二芳基乙基)酰胺18环化为3, 4-二氢异喹啉衍生物19和随后的亚胺的分子内原位N-烷基化。还介绍了容易获得的平面8,9-二烷氧基化苯并[c]菲啶鎓盐。在氯化钛(IV